We have a Freedom 39 Deck Salon, with two "saddle tanks" for water, one on either side of the cabin behind the setees. We believe they are about 90 gallons each. They are attached through the outlet hoses when both selection valves are open. When we slowly fill one tank, both tanks fill. However, when the guys here in Ensenada MX glug in the 20 liter jugs, the dock side fills up, and the level doesn't equalize until overnight, leaving us half full. We'd rather not have the guys haul the jugs to the other side to fill, it's heavy work and they don't wear non-marking shoes. For right now, we just tank up more frequently. Anyone have a better idea?

Try opening up the fill on both sides to let more air out. Maybe that will help a bit; but I bet the interconnecting pipes are a lot smaller than the fill pipes, taking a long time to equalize across the boat.

I think that opening the fill cap for the other tank is a good idea, but you shouldn't need to do that as it has its own vent line. But perhaps that vent line is clogged. Is there a valve between the 2 tanks that isn't open all of the way?

Personally I just have the water guys place the water jugs on the dock side of the boat and then move them to the fill side. They're not that heavy.